If you have a roof, you should be collecting rainwater. It requires no “softener,” uses less soap, and is friendlier to work with than even the best water that has come into contact with the ground. Grandmother loved the softness of rainwater for washing her hair, and the country house always had a barrel — topped with some screening to keep out leaves — standing under eaves near the gutter downspout.

You will need the following materials:

A barrel, cistern, or tank

Guttering

A downspout from the gutter into the tank

Hardware, such as elbows, pipes, and pipe cement, to connect the spout to the tank

A “roof washer” to divert the first flow of dirty water away from the tank (see illustration)

A tank overflow pipe to direct water away from your foundation

A faucet for the bottom of the tank

A tight-fitting, childproof, removable cover that will keep out mosquitoes and allow access for cleaning

Hoses or watering cans to take water from the faucet to the garden or wherever it is needed

Cut a hole in the lid of a large, heavy-duty trash can, then place the can under the drainpipe of your gutter to collect water. Fasten some fine mesh screen under the hole to keep debris out. The illustration shows a simple system for dumping the leaves and dirt that collect on a roof before sending cleaner water to the cistern. You can construct a more elaborate filter by filling a tank or barrel with alternate layers of coarse gravel, charcoal, and sand to cleanse the water before sending it to the house. All filters should be drained and cleaned when not in use.

If you want to use roof-collected water for washing up, brushing your teeth, or drinking, it’s a good idea to filter it and then boil it for two minutes first, or use chemical treatment. At my home we use an AquaStar® ceramic filter that sits in the kitchen as a water dispenser.

If your house doesn’t have gutters, maybe it’s time to think about adding them. An alternative is to construct a shed roof over a cistern tank at a high point of land and collect water there, then send it by gravity and pipe to your home. Enameled steel makes a good shed roof that stays cleaner.

As with any water collecting area, including swimming pools, ponds and bathtubs, you will always need to install an overflow drain, or wish you had. With a rain barrel or cistern, it is good to have that drain be a two-inch (5 cm) diameter pipe that exits the container wall somewhere near the top and deposits excess water downhill, preferably a receptive and water-tolerant garden bed.

It is difficult to understate the importance of always having a supply of potable water in storage. A starving animal can live even if it loses nearly all its glycogen and fat, as well as half its body protein, but a loss of 20 percent of body water results in death. A person can live without food for over a month, but without water they will expire in a few days. The human body is made up of about 65 percent water.

Less than one hundredth of 1 percent of this blue planet’s water is sweet enough to drink and regularly renewed by rainfall. Just this tiny fraction sustains fields, forests, wetlands, grasslands, and all terrestrial life.

Foolishly, civilization has been ruining its most vital asset, and the pace of destruction is accelerating. Falling water tables, altered and contaminated river flows, shrinking lakes, disappearing mangrove swamps, and “dead zones” in our oceans should warn us, but these warnings are being ignored. We still use rivers for irrigation until they are too dry to reach the sea; still build enormous dam and diversion projects; still drain aquifers at unreplenishable rates; and still dump our sewage, garbage, and toxic chemicals into our drinking water.

Global warming will soon bring the situation to a head for many nations. Glaciers and mountain snow packs are retreating. A temporary surge of melt water creates water abundance for cities and towns downstream, lulling them into false security. Then it will be gone, and with it, the ability of large populations to live downstream.

So what should we be doing? Every individual should first, and most importantly, identify and protect a secure supply of water. If we follow the recommendations that each person drink eight glasses of water a day, that’s 8 times 8 ounces or 64 ounces per person — two quarts (1.9 liters) of water per person per day for drinking.

Allow an equal amount for cooking, brushing teeth, and minimal cleaning up and you need four quarts or one gallon (3.8 liters) of water per person per day.

For two persons, two gallons. For a family of four, four gallons. For a three-day weekend, the family of four needs 12 gallons. For 30 days, a family of four would need 120 gallons (454 liters)! And this is rationing the amount of water used at all times. No toilet-flushing or clothes-washing is included in calculating minimum water needs.

Since most people live in or close to cities, they are likely to be dependent on municipal water systems. Municipal systems are almost never solar powered. They run on electricity, and, unless you are in Iceland or Scotland, the electricity likely comes from oil, gas, coal, nuclear, or hydro. Only the last of those is a renewable resource, if it can be maintained. The rest will become increasingly scarce.

In 1997 Jacques Yves Cousteau told a UN gathering, “The future of civilization depends on water. I beg you all to understand this.” That’s still good advice today.

Albert Bates was a civil sector representative at the Copenhagen climate conference, trying to point the world back towards a stable atmosphere using soils and trees. His books include Climate in Crisis and The …

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